1. Field of the Invention
The present invention relates to a film forming method of forming a diamond-like carbon film on a workpiece installed in a reactor, and a plasma chemical vapor deposition apparatus used in the film forming method.
2. Description of Related Art
An example of a plasma chemical vapor deposition apparatus (hereinafter, also referred to as “PCVD apparatus”) is described in Japanese Patent Application Publication No. 2004-47207 (JP 2004-47207 A). The PCVD apparatus includes a reactor to which a process gas is supplied, a waveguide for supplying microwaves, and a dielectric window for closing an opening provided in a side wall of the reactor. In the reactor, the dielectric window supports a workpiece, and outside the reactor, the tip end of the waveguide is in contact with the dielectric window.
As microwaves propagate from the waveguide to the surface of the dielectric window, the process gas is decomposed into plasma in the vicinity of the dielectric window in the reactor. In addition, as the decomposed process gas adheres to the workpiece, a film based on the gas is generated on the workpiece.
The formation of a diamond-like carbon film (hereinafter also referred to as “DLC film”) on the workpiece can be realized by supplying a hydrocarbon gas such as acetylene as the process has into the reactor, and decomposing the hydrocarbon gas into a plasma.
However, the DLC film may be formed on a member which requires both high hardness and a low coefficient of friction, such as a plunger of a high-pressure fuel pump provided in a fuel supply system of an internal combustion engine, in particular, it is desirable for the DLC film formed on the plunger to achieve both high hardness and a low coefficient of friction to a high level.